Archive for the Tourmaline Group Category

Tourmaline Group

Refractive Index : 1.644 – 1.624 + 0.134 – 0.021

Optical Characteristic : DR U-

Specific Gravity : 3.06 + 0.20 – 0.06

Formula : Na(Li,AI)3AI6(BO3)3Si6018(OH)4

Crystal System : Trigonal

Variety/Species : All

Species/Group : Tourmaline Group

Birefringence : 0.018 to 0.040

Dispersion : 0.017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert to weak

UV Short : Inert [...]

Watermelon Tourmaline

Refractive Index : 1.644 – 1.624 (+ 0.011 – 0.009)

Optical Characteristic : DR, U-

Specific Gravity : 3.06 + 0.20 – 0.06

Formula : Na(Li,AI)3AI6(BO3)3Si6018(OH)4

Crystal System : Trigonal

Variety/Species : Elbaite

Species/Group : Tourmaline Group

Birefringence : 0.018 to 0.040

Dispersion : 0.017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert to weak

UV Short : Inert [...]

Uvite

Refractive Index : 1.660 – 1.612

Optical Characteristic : DR, Uniaxial negative

Specific Gravity : 3.06 (- 0.20 – 0.06)

Formula : CaMg3(AI5Mg)BSi6O27(OH)3(OH,f)

Crystal System : Trigonal

Variety/Species : Tourmaline

Species/Group : Tourmaline Group

Birefringence : 0.017 to 0.021

Dispersion : 0.017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert to weak

UV Short : Inert to weak

Pleochroism : [...]

Verdelite

Refractive Index : 1.644-1.624 (+.011 -.009)

Optical Characteristic : DR, uniaxial negative

Specific Gravity : 3.06 (+.20 -.06)

Formula : Na(Li,AI)3AI6(BO3)3Si6018(OH)4

Crystal System : Trigonal

Variety/Species : Elbaite

Species/Group : Tourmaline Group

Birefringence : .018 to .040

Dispersion : .017

Hardness : 7 to 7.5

Toughness : Fair

Ultrasonic : Risky

Steam : Risky

UV Long : Inert

UV Short : Inert

Pleochroism : 2 colors

Strength : Weak to strong

Pleochroism [...]